This invention relates to an arrangement for monitoring the temperature of a moving component, for example, for monitoring the oil temperature of a rotating hydraulic coupling. In this type of monitoring arrangement, when a preset temperature limit is attained, a temperature sensor arranged on the moving component operates a signal or some other responsive means associated with the moving component.
It is advisable to monitor the temperature of moving machine parts which under certain circumstances can be subjected to relatively high thermal loading during operation. In order to prevent damage to or failure of such machine parts, when a permitted temperature limit is exceeded, it is often necessary to switch off the machine drive or to take other appropriate steps.
Temperature problems of the above described kind arise, for instance, in hydraulic couplings, where an extremely rapid rise in temperature can be caused, especially during overloading and when a jam occurs. For this reason, it is advisable to monitor the oil temperature in the coupling so that suitable safety precautions can be initiated when there is an unacceptable rise in the oil temperature. For this purpose, temperature sensors are already known. They are typically installed in a housing wall of a hydraulic coupling and are held in place by a sweated or soldered joint which melts at a predetermined temperature. As soon as the sweated or soldered joint melts due to the temperature limit in the coupling being exceeded, a spring installed in the temperature sensor actuates a piston which can travel out sufficiently far to actuate a corresponding switching device which is adapted to initiate appropriate subsequent measures for the particular installation. In many cases, the appliance being monitored is simply switched off which permits location and removal of the cause of overheating.
Known temperature sensors of the above noted type have the inherent disadvantage that they are very expensive to manufacture and are reliable only to a relatively limited extent. Their relatively complicated construction inevitably means that despite the exercise of the greatest care and precision during manufacture, over a long operating period, reliable temperature sensor response cannot be guaranteed.
The above described temperature sensors have the further disadvantage that after each time one of them responds, a new temperature sensor has to be installed, since the temperature sensor is destroyed by each response. When a new temperature sensor is installed, not only is valuable working time taken up, but it may also be necessary to carry out rebalancing, especially in relatively fast-running machines.
The above-mentioned technical disadvantages enable only relatively expensive plants to be monitored with this type of temperature sensor, since it is too expensive to equip smaller and less expensive plant with the sensors. For many applications, moreover, the monitoring of temperature using a sensor which is destroyed when it responds is basically unacceptable.